MICRO ENTORNO

Several methods exist for the prevention of mosquito bites in the U.S. and the DR Insect repellants, destruction of breeding sites, mosquito nets, widespread spraying of insecticides on the part of the government, bite-resistant clothing, the introduction of biological controls to breeding sites, properly screened windows, and the sterile insect technique are all possible options for the reduction of mosquito populations, and in turn, the incidence of mosquito borne diseases. While measures like insect repellant and bite-

resistant clothing do help in reducing the risk of being bitten, the elimination of breeding reservoirs is one of the most effective means of reducing mosquito populations. On La Reunion, the use of insect repellant and insect repellant devices (like electrical coils) did not serve to significantly decrease the chance of an individual or household member contracting the disease (Staikowsky et al., 2008). Pending the development of a widely distributed vaccine, this ineffectiveness again reinforces the need for the avoidance of mosquito bites as a primary means of disease prevention, mostly through the destruction of breeding sites and mosquitos. Community education programs about eliminating potential breeding sites have been pursued in the past in an effort to combat other mosquito-borne diseases like Dengue and have proven effective in some instances (Gordon, Rojas, & Tidwell, 1990, p. 195). Countermeasures include the elimination of features of the urban environment that are conducive to the reproduction of mosquitos: properly drained gutters, reliable provision of clean drinking water that would remove the need for large water storage containers in individual households, and regular collection of garbage and other debris that can create pools of standing water. In those cases where water containers will be present, properly covering them or treating them with larvicides can help reduce the breeding population of mosquitos. Community-based interventions have proven to be more effective in control of mosquito populations than intense, and less frequently administered control activities on the part of government agencies. These community-based approaches that focus on education and sustainability have proven effective in the control of Ae. aegypti in Cuba, where the measures were implemented to help reduce the incidence of dengue (Toledo et al., 2007). Surveillance of travelers returning from visiting areas in the Caribbean where CHIKV is present could potentially

ensure the disease does not become endemic in these regions (Morens & Fauci, 2014, p. 886). Similarly, developing rapid tests that can detect the presence of the disease in an infected individual early in those areas where CHIKV is in circulation allows for the isolation of the individual, ideally preventing them from being further bitten and transmitting the disease to others.

An approach that could also be used in addition to community education initiatives is the application of biological controls, such as bacillus thuringiensis, larvivorous fish and snails, and nematodes. These are better suited to those environments where it is difficult to impose government oversight as a means of insuring compliance with vector control measures, and can be actively applied in those areas where outbreaks rapidly increase in severity. It can serve as a compliment to community education efforts about more passive but pervasive means of prevention (Gordon et al., 1990, p. 206). During extremely severe and widespread outbreaks like the one on La Reunion, the use of mosquito repellant was found to not have a significant effect in reducing infection rates, most likely because any lapse in vigilance with the application would result in infection (Staikowsky et al., 2008, p. 203). There is also a third method of vector control, one that ingeniously uses pre-existing populations of mosquitos to prevent further reproduction.

The sterile insect technique entails the release of large numbers of sterilized male mosquitos into the environment, where they breed with potentially infected females that then die before being to encounter a fertile male. This method has been used effectively in controlling screwworm flies, fruit flies, and moths in a variety of environments. The newest application of this idea is called RIDL, (release of insects carrying a dominant

lethal). Males are not sterilized but instead genetically engineered to be homozygous for a lethal allele, which when expressed in heterozygous offspring created breeding with wild, infected mosquitos leads to death. This method of control is extremely promising, but has yet to be tested in earnest and requires significant biomedical technology and government funding (Wilke et al., 2009, p. 69). For this reason, it would be difficult to deploy on a large scale in developing nations. Vector distribution is also a key component in understanding the epidemiology of CHIKV, the impact it has already had on the Americas, and the threat it poses to other regions with unexposed populations that frequently travel to areas where the virus is active.

The vector distribution is affected by a number of factors. Ae. aegypti is most commonly found in urban environments where water pools in containers and other receptacles. In the case of the DR, these are often the large 55-gallon drinking containers many families keep near their home for a steady supply of potable water. Development and periurban settings increase the number of breeding sites for Ae. aegypti. Howell and Chadee (2006) have shown that homes in urban areas in the DR have higher numbers of resting mosquitos than those in rural areas and increasing urbanization will produce conditions even more favorable to the proliferation of Ae. aegypti, in areas where population densities are highest (p. 71). Again, the intertwined nature of the biological, economic, and social is illustrated. Economic development in the DR is increasingly geared toward enterprises that are predicated on increased urbanization, such as tourism and the creation of IFZ’s (Ferguson, 1992).